In a known automatic turning machine of this kind, the work transfer means is equipped with a revolving unit which revolves a partially machined workpiece, removed from one of the clamping devices, and inserts the machined end of said workpiece into the same clamping device once again. In order that this clamping device be in a position to clamp the workpiece at the end which has a reduced diameter due to the preceding machining, a reducing sleeve is pushed into the clamping device from the rear before the workpiece is once again inserted into said clamping device, and furthermore an adjustable stop for the workpiece is introduced into the clamping device, likewise from the rear, in order to secure the clamping position of said clamping device in an axial direction.
In these known automatic turning machines, the revolving unit connected with the work transfer means requires considerable construction expenditure and space; the same is true of devices which are required for the automatic insertion and withdrawal of the reducing sleeves and stops. The arrangement of clamping devices exclusively on the side of the work turret which faces the charging device also means that all machining devices must be disposed in the neighbourhood of this one side of the work turret, which can lead to considerable space problems.
It is true that automatic turning machines are also known as in German Patent-Auslegeschrift 1552 250, which have a pair of clamping jaws on each of a multiplicity of clamping devices disposed on the periphery of a work turret, said clamping jaws clamping a workpiece in its middle area in order that both ends be machined simultaneously by machining devices disposed on both sides of the work turret. However, in this case, a workpiece partially machined during a first revolution of the work turret cannot be clamped in another position for additional machining of its middle area on a second revolution of the work turret. If such an additional machining is necessary, the workpiece must be passed to a clamping device which is independent of the work turret.